ACIER INOXYDABLE MARTENSITIQUE

MARTENSITIC STAINLESS STEEL

Abrégé anglais

A substantially martensitic stainless steel as cast having good castability,
ductility and capability of being hardened to a wide range of hardness, the
steel
consisting essentially of, in weight percent, up to about 0.08 % carbon, about
1.0
to about 4.0 % manganese, about 13.0 to about 17.0 % chromium, about 1.5 to
about 4.0 % copper, up to about 0.12 % nitrogen, less than about 1.0 %
silicon,
less than about 1.0 % molybdenum, less than 1.0 % nickel, less than about 0.03
% phosphorus, less than about 0.5 % sulfur, up to about 0.005 % boron, up to
0.5 % niobium, vanadium, titanium and / or zirconium and balance essentially
iron. The steels have particular utility in the production of cast golf clubs,
forged
golf clubs, cutlery, boat propellers and other cast, forged and wrought
products,
including free machining materials.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows:
1. A substantially martensitic stainless steel
composition consisting essentially of, by weight percent, up
to about 0.08% carbon, about 1% to 4% manganese, about 13.0%
to about 17% chromium, about 1.5% to 4.0% copper, about
0.04% up to about 0.12% nitrogen, less than about 1.0%
silicon, less than about 1.0% molybdenum, less than 1.0%
nickel, less than about 0.03% phosphorus, less than about
0.5% sulfur, up to about 0.005% boron, and balance
essentially iron.
2. The stainless steel composition of claim 1 having
about 0.03% to 0.07% carbon, about 1.5% to about 3.5%
manganese, about 14.0% to about 16.0% chromium, and about
2.0% to about 3.5% copper.
3. The stainless steel composition according to claim
2 having about 1.75% to about 3.0% manganese, about 0.03% to
about 0.06% carbon, about 0.06% to about 0.09% nitrogen, and
about 2.5% to about 3.25% copper.
4. The stainless steel composition according to claim
1, wherein said silicon is less than about 0.75%, said
nickel is less than about 0.5%, said molybdenum is less than
about 0.5%, said boron is less than about 0.003%, said
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phosphorus is less than about 0.025%, and said sulfur is
less than about 0.030%.
5. A substantially martensitic stainless steel
composition consisting essentially of, by weight percent,
up to about 0.08% carbon, about 1% to 4% manganese, about
13.0% to about 17% chromium, about 1.5% to 4.0% copper,
about 0.04% up to about 0.12% nitrogen, less than about
1.0% silicon, less than about 1.0% molybdenum, less than
1.0% nickel, less than about 0.03% phosphorus, less than
about 0.5% sulfur, up to about 0.005% boron, up to about
0.5% of one or more of niobium, titanium, vanadium or
zirconium, and the balance essentially iron.
6. A substantially martensitic stainless steel article
having a hardness on the Rockwell scale of about B 95 to C
40 or higher and consisting essentially of, in weight
percent, up to about 0.08% carbon, about 1.0% to about 4.0%
manganese, about 13.0% to about 17.0% chromium, about 1.5%
to about 4.0% copper, about 0.04% up to about 0.12%
nitrogen, less than about 1.0% silicon, less than about 1.0%
molybdenum, less than about 1.0% nickel, less than about
0.03% phosphorus, less than about 0.5% sulfur, up to about
0.005% boron, and balance essentially iron.
7. The steel article of claim 6 wherein said article
includes sheet, strip, bar, rod, wire, tubing, remelt stock,
shaped, forged, cast, and powder articles.
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8. The martensitic stainless steel article of claim 6
having about 0.03% to about 0.07% carbon, about 1.5% to
about 3.5% manganese, about 14.0% to about 16.0% chromium,
and about 2.0% to about 3.5% copper.
9. The steel article of claim 6 having about 1.75% to
about 3.0% manganese, about 0.03% t:o about 0.06% carbon,
about 0.06% to about 0.09% nitrogen, and about 2.5% to about
3.25% copper.
10. The steel article of claim 6 wherein said silicon
is less than about 0.75%, said nickel is less than about
0.5%, said molybdenum is less than about 0.5%, said boron is
less than about 0.003%, said phosphorus is less than about
0.025%, and said sulfur is less than about 0.03%.
11. A stainless steel golf club head which is
substantially martensitic having a hardness in the Rockwell
range of B 95 to about C 40 or higher, said golf club head
consisting essentially of, in weight percent, up to about
0.08% carbon, about 1.0% to about 4.0% manganese, about
13.0% to about 17.0% chromium, about 1.5% to about 4.0%
copper, up to about 0.12% nitrogen, less than about 1.0%
silicon, less than about 1.0% molybdenum, less than 1.0%
nickel, less than about 0.03% phosphorus, less than about
0.03% sulfur, up to about 0.005% boron, and balance
essentially iron.
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12. A free machining substantially martensitic
stainless steel composition consisting essentially of, in
weight percent, up to about 0.08% carbon, about 1.0% to
about 4.0% manganese, about 13.0% too about 17.0% chromium,
about 1.5% to about 4.0% copper, about 0.04% up to about
0.12% nitrogen, less than about 1.0% silicon, less than
about 1.0% molybdenum, less than 1.0% nickel, less than
about 0.03% phosphorus, about 0.1% up to about 0.5% sulfur,
up to about 0.005% boron, and balance essentially iron.
13. The free machining stainless steel composition of
claim 12 having about 0.03% to 0.07% carbon, about 1.5% to
about 3.5% manganese, about 14.0% to about 16.0% chromium,
and about 2.0% to 3.5% copper.
14. The free machining stainless steel composition of
claim 13 having about 1.75% to about 3.0% manganese, about
0.03% to about 0.06% carbon, about 0.06% to about 0.09%
nitrogen, and about 2.5% to about 3.25% copper.
15. The stainless golf club head of claim 11 consisting
essentially of, in weight %, about 0.03% to about 0.07%
carbon, about 1.5% to about 3.5% manganese, about 14.0% to
about 16.0% chromium, about 2.0% to about 3.5% copper, and
about 0.04% to about 0.12% nitrogen.
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16. The stainless golf club head of claim 11 consisting
essentially of, in weight %, about 0.03% to about 0.06%
carbon, about 1.75% to about 2.5% manganese, about 14.5% to
about 15.5% chromium, about 2.5% to about 3.25% copper,
about 0.06% to about 0.09% nitrogen, about 0.5% max nickel,
about 0.75% max silicon, about 0.5% max molybdenum, about
0.025% max phosphorus, about 0.001% to about 0.003% boron,
and balance essentially iron.
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Description

20~~5154
MARTENSITIC STAINLESS STEEL
FIELD OF TI1E INVENTION
The present invention relates to a novel alloy composition having
controlled hardness and good casting characteristics. The alloy is useful for
applications where the material is cast or forged into articles such as golf
clubs
and boat propellers. The alloy is also useful for wrought applications
including
free machining and cutlery applications.
BACKGROUND OF THE INVENTION
Martensitic stainless steels are typically in the lower range of chromium
for stainless steels and therefore lower in corrosion resistance compared to
the
other stainless steels. Martensitic stainless steels can be heat treated to a
wide
1 5 range of strengths and have good machinability when sulfur is added and
the
steels are in the heat treated condition. Martensitic stainless steels are
usually
easy to heat treat and relatively ease to hot and cold work. Typically, the
martensitic stainless steels are heated to a high temperature, such as 1700 to
2000°F ( 930 to 1095 °C ) and then air or oil quenched. A second
heat treating
2 0 step from 800 to 1400'°F ( 425 to 760 °C ) tempers the
martensitic stainless to
the desired strength level. Martensitic stainless steels generally tend to be
lowest cost of all the stainless steels.
Materials used for manufacturing golf club heads have varied
considerably over the past several decades. Stainless steels, carbon steels
and
2 5 many other alloys have been used for' golf club heads to provide the
desired
combination of hardness, weight, ductility, corrosion resistance, strength,
toughness, abrasion resistance, wear resistance and resilience. Various alloys
have also been used for the shaft of golf clubs which may have different
property
requirements than the heads of the golf clubs.
3 0 The alloys used for golf club heads were initially well known materials
used in sand and investment foundries; for casting. Other club manufacturers
have chosen to go the route of forged clubs which require more finishing work.
Familiarity and availability were the main reasons many of the foundries used
specific stainless steel alloys rather than designing a composition for the
golf
3 5 head properties. Recently, club designers have experimented with new
unusual
alloys which were more expensive but offered specific properties, such as
better

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2;055154
feet or hardness. The properties of the various alloys for golf clubs were
also
modified by heat treatments to develop increased hardness or strength.
When it comes to the selection of a club material, some manufacturers
have spared no expense if the club ca,n provide added feel or distance for the
S golfer. More expensive alloys such as copper- beryllium, copper-tin, copper
nickel-zinc and aluminum-titanium have been used as well as surfaces having a
composite structure with fibers impregrnated.
Golf club heads may be forged o~r cast. The use of investment cast heads
allows the club manufacturers to purchase detailed castings which require no
or
1 0 minimal finishing operations. The freE~dom in design is greatly increased
with
the use of castings. Casting tooling includes the hosel detail, scoring lines
and
identification as part of the mold. Forged clubs are more limited in design
and
require considerable finishing operations. Forging tooling is far more
expensive
if club design changes are required. Forged articles generally would have a
1 5 higher density because of the working of the material. The amount of
forging
reduction has a strong influence on the metallurgical structure. Forgings may
also be produced at manufacturing plants which do not have melting or casting
equipment. The properties requiremenia for golf club heads permit either cast
or
forged production.
2 0 The selection of a material for a golf club head must consider many
properties. The finished head weight must fall within very narrow limits to
comply with specifications. The metal must be capable of withstanding the wear
and impact forces associated with playing the game. The tensile strength,
fracture resistance, hardness and density of a material must all be considered
in
2 5 selecting a material for casting.
Stainless steels are used for golf clubs because they provide the above
properties and also have excellent corrosion resistance. The most common
choices of stainless steels have been T304, T431 and 17-4PH. Each of these
materials offers different properties.
3 0 T304 is an austenitic material having about 18 % Cr, 8 % Ni and less than
0.08 %C. This stainless is relatively soft and can not be hardened by heat
treatment. While very corrosion resistant, its use is restricted to irons
having
thicker hosel bases which helps to limit the amount of bending. Austenitic
stainless steels, such as T304, have been used but tend to mar very easily.
3 5 Often these steels were selected because scrap was available at a
reasonable
price. The austenitic stainless steel;; have a large addition of nickel which
2

_- 2 0 5 51 5 4
greatly increases the cost of the material. The lower strength level as cast
does
not allow a more streamlined golf head de;>ign to be used.
The 400 series of stainless steels has also been used to provide the
desired hardness and corrosion resistance for golf clubs. However, these
alloys
require a suitable heat treatment and close control of chemistry to achieve
the
desired properties. Type 431 is commonly used and requires a double heat
treatment to obtain the desired properties. The steel lacks the ductility
required
for adjusting the alignment of the head .and the hosel. T431 is a martensitic
stainless consisting of about 16 % Cr, 2 °~°Ni and less than 0.2
% C. It is less
1 0 corrosion resistant than T304 and is usually given a passivation treatment
to
clean the surtace. T431 can be heat treated to provide high strength and
hardness levels and is restricted for use in wedges, putters and ironheads.
The stainless steel widely used for golf clubs has been 17-4 PH ( see
U.S. Patent Nos. 2,482,096; 2,482,097 a,nd 2,482,098 ) . It has the desired
1 5 corrosion resistance and a hardness in the Rockwell C range of about 30 to
35.
It can not be sofened to a significantly lower level to obtain the desired
feel when
striking the ball. This steel was designed originally for aircraft
requirements and
was not designed for the properties needE3d for the golfing industry. Many
golf
club heads have been designed using 1 i'-4PH steel simply because it is well
2 0 known, available as remelt stock and is forgiving of minor chemistry
variations.
17-4PH is a precipitation hardenable steel having about 17 % Cr, 4 % Ni, 2.75
Cu and less than 0.07 % C. It is the strongest and hardest of the stainless
steels
presently used for this application .
Some club designers have used chromium plated clubs but these tend to
2 5 show corrosion when dinged.
One alloy designed specifically for tree golfing industry is described in U.S.
Patent No. 4,314,863 by Jon McCormick of Fansteel Inc. The stainless steel
casting alloy consisted of 13 to 19 % chromium, 2 to 3.6 % nickel, 2 to 3.5
copper, 0.20 to 1.4 % manganese, 0.5 to 1.0 % silicon, 0.1 to 0.8 % carbon,
0.10
3 0 % max nitrogen, less than 0.10 % molybdenum, less than 0.10 % aluminium,
less
than 0.10 % columbium, 0.035 % max sulfur, 0.035 % max phosphorus and balance
essentially iron. The sum of nickel and copper must be at least 5 %. The
stainless
casting was designed to be economical, to provide the desired hardness of
about
Rockwell B 90 and to provide other mechanical properties without requiring any
3 $ supplemental heat
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treatments. The preferred micro;>tructure is substantially austenite in
combination with some martensite or delta ferrite.
Another stainless steel developed for the golf club head industry is
disclosed in Japanese publication J55029329. The alloy is designed to produce
good vibration dampening and has a composition comprising 8 - 25 %Cr, 0.2
3.0 %Mo, 0.5 - 3.0 %Ni, 1.0 - 4.0 %Si, 0.06 %maxC, and balance Fe. The typical
alloy had about 18 %Cr, 1 %Mo,1 %Ni" 2.5 %Si, 0.005 %C and balance Fe. The
main improvements in dampening were attributed to the additions of Cr and Mo.
Stainless steels are widely used in marine applications because of their
1 0 excellent corrosion resistance. Alloys such as T431, 15 - 5 PH, and 17 - 4
PH
are widely used for applications such as boat propellers. Marine applications
also require alloys which have good ductility, strength and hardness. However,
the PH alloys are over-graded for thesE: uses and there exists a need for a
more
cost effective and easier to heat treat alloy.
1 5 Martensitic stainless steels have been developed for the marine industry
which possess good pitting resistance and high strength. An example is
Japanese publication J 01246343 which comprises up to 0.08 % C, up to 3
Si,upto3%Mn,2.5-5.0%Cu,2.5-6.0%Ni,10.0-20.0%Cr,l.5-5.0%Mo,
0.1 -1.0 % Nb and/or Ta, 0.005 - 0.05() % B, 0.105 - 0.40 % N and balance Fe.
2 0 The alloy was for use as marine pumps, shafts and valves.
Another martensitic stainless for marine applications is represented by
Japanese publication J 63000436. The steel comprises 0.03 % max C, 0.30 -
0.60%Si,0.7-1.00%Mn,0.15-0.4:5%Ni,11.5-12.5%Cr,0.5%maxMo,
0.30 - 0.50 %Cu, 0.060 % N and balance Fe. The alloy has good welding
2 5 characteristics including the capability of being welded without
preheating.
None of the alloys presently used for golf clubs have the desired
combination of properties to be capable of providing the complete production
of
all of the desired clubs and designs. Furthermore, the expense of the
materials
and the cost of the required heat treatments or finishing steps results in the
need
3 0 for a more economical alloy with the dlesired range of properties. The
existing
metals used for the manufacture of golf club heads are expensive and deficient
in one or more properties and have additional processing steps required to
enable its use.
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2055154
SUMMARY OF THI= INVENTION
The present invention comprises a substantially martensitic, as-cast,
stainless steel composition which may be processed into cast, forged and
wrought articles manufactured from the steel composition. The composition
consists essentially of, in weight %, up to about 0.08 % carbon, about 1.0 %
to
about 4.0 % manganese, about 1.0 % max silicon, less than 1.0% nickel, less
than 1.0 % molybdenum, about 1.5 to about 4.0 % copper, up to about 0.12
nitrogen, about 13.0 to about 17.0% chromium, boron up to about 0.005 %,
1 0 sulfur up to about 0.5 %, phosphorus up to about 0.03 % and balance
essentially
iron with normally occurring residuals.
The stainless steel composition of the present invention is particularly
suited for investment cast and forged golf club heads and boat propellers as
well
as many other wrought, forged and cast articles. The economical cast or forged
1 5 articles have a combination of properties well suited for golf clubs.
These
include good corrosion resistance, good ductility, the ability to be hardened
within the range desired for better "feel" and good castability.
For marine applications, the alloy has excellent strength, corrosion
resistance and hardness necessary for articles such as propellers for boats.
2 0 For free machining grades, the present steels are characterized by a
sulfur addition up to about 0.5 % and typically about 0.10 % to about 0.5 %.
The composition of the present invention also has very good wrought
properties which include good ductility, grain size and strength.
The stainless steel of the present invention is characterized by a cast
2 5 substantially martensitic structure having less than about 20 % ferrite
and less
than about 5 % retained austenite. The amount of ferrite in the final product
will
depend on the heat treatment selected.
An object of the present invention is to provide martensitic stainless steel
castings, forged articles and wrought products which have the capability of
3 0 being heat treated to a broad range of hardness.
A further object is to provide an alloy which is less costly to produce yet
provides better properties than existing mal:erials.
A still further object of the present invention is to provide a stainless
composition which is balanced to provide better castability and hot working.
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2055154
An advantage of the present invention is the production improvement
provided by the composition balance which provides improved ductility in cast
and wrought products.
A further advantage of the present invention is the reduction of cracking in
the cast articles.
A still further advantage is the greater range of hardness which can be
provided with the steels of the present invention to provide golf heads with
better
feel.
Another advantage of the steels of the present invention is the improved
1 0 ductility which simplifies the manufacturing of the connection between the
head
and the hosel to allow the desired club angle.
The objects and advantages listed above and others will become better
understood based on the detailed description of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The martensitic stainless steel of the present invention was developed to
provide a combination of properties particularly suited for the production of
cast
2 0 or forged golf club heads. The propE;rties for which the alloy was
particularly
designed for included a hardness within the range of Rockwell B 95 to Rockwell
C 40 or higher, good castability, good ductility, good toughness and
acceptable
corrosion resistance. The present alloy provides this combination of
properties
and is more economical than existing materials and their required processing
2 5 steps for club manufacturing. The steels of the invention may be used to
provide
the desired combination of properties using a single heat treatment that does
not
require age hardening. Numerous articles may be manufactured from the
stainless steel composition of the invention. These include various finished
wrought product articles such as sheet, strip, bar, rod, wire, tubing and
wrought
3 0 semi-finished articles such as remelt :>tock, slabs, billets, blooms, and
shaped
articles. Other articles from the composition of the invention include forged,
cast
and powder articles. Specific articles of interest relating to the steels of
the
invention include cast products such as golf club heads and propellers, forged
products such as golf club heads and cutlery, and stainless steel articles for
free
3 S machining applications.
The composition of the substantially martensitic stainless steel of the
invention consists essentially of, in weight percent, up to about 0.08 %
carbon,
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2055154
about 1.0 to about 4.0 % manganese, about 13.0 to about 17.0 % chromium, about
1.5 to about 4.0 % copper, up to about 0.12 % nitrogen, less than 1.0 %
nickel, less
than about 1.0 % silicon, less than about 1.0 % molybdenum, sulfur up to about
0.5
and balance essentially iron. The steels will have the normally occurring
residual
elements present from the melting practice. These will include phosphorus up
to
about 0.03 % and other residual elements. A small addition of boron up to
about
0.005 % may be made. Sulfur may be added up to about 0.5 % and preferably
about 0.1 to about 0.5 % for free machinirng applications. Sulfur will
normally be
below about 0.03 % when machinability is not important. Niobium, titanium,
1 0 vanadium and or zirconium may be added in amounts up to about 0.5 %,
preferably
up to 0.3 % for grain refinement and improved ductility.
A preferred composition of the steel of the invention consists essentially
of, in weight %, about 0.03 to about 0.07 % carbon, about 1.5 to about 3.5
manganese, about 14 to about 16 % chromium, about 2 to about 3.5 % copper,
1 5 about 0.04 to about 0.12 % nitrogen, less than about 0.9 % and more
preferably
less than about 0.75 % nickel, about 0.001 to about 0.003 % boron, and balance
essentially iron. Any of the preferred ranges for the elements may be used
with
the broad ranges for the remaining elements.
A more preferred range of the steels of the invention for the golf club
2 0 market consists essentially of, in weight °/~, about 0.03 to about
0.06 % carbon,
about 1.75 to about 2.5 % manganese, about 14.5 to about 15.5 % chromium,
about 2.5 to about 3.25 % copper, about 0.06 to about 0.09 % nitrogen, about
0.5 % max nickel , about 0.75 % max silicon, about 0.5 % max molybdenum,
about 0.025 % max phosphorus, about 0.02 % max sulfur, about 0.001 to about
2 5 0.003 % boron and balance essentially iron. Any of the more preferred
ranges
of elements may be used with the broader ranges of the remaining elements.
The carbon content of the stainless steel composition is maintained below
about 0.08 % to provide good corrosion resistance, good ductility, good
castability and the desired hardness. With the carbon maintained at these low
3 0 levels, the alloy may be properly balanced) with the present chromium
levels to
produce the desired martensitic structure. The lower chromium levels provide
the desired corrosion resistance and help make the alloy more economical to
produce. The preferred carbon levels of about 0.03 to about 0.07 % and more
preferably from about 0.03 % to about 0.06 %, contribute to the desired
3 5 combination of properties. This carbon content is a departure from many of
the
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2055154
stainless steel alloys designed for they golfing industry, such as taught in
U.S.
4,314,863, wherein the carbon is maintained above 0.2 % and typically about
0.2 to 0.5 %. The present alloy avoids the presence of excessive carbides
which
lower corrosion resistance, reduce ductility, lower notch toughness and make
machining more difficult. The high levsrl of carbon in this reference was
required
to achieve the desired as-cast hardness.
The nitrogen levels present in the steels of the invention are balanced
with the carbon content to provide the desired martensitic structure as cast.
A
nitrogen content up to about 0.12 % may be used. A preferred range of about
1 0 0.04 to about 0.12 % and more preferably about 0.06 to about 0.09 %
provides a
more controlled balance of the desired properties. Like carbon, the nitrogen
adds to the hardness of the alloy, permits a lower nickel content without
lowering the corrosion resistance to an~~ significant degree and reduces the
cost
of the alloy.
1 5 The manganese content of the present steel is typically about 1.0 to about
4.0 % and preferably about 1.5 to about 3.5 % for the preferred properties.
Optimum contents range from about 1.T5 to about 3.0 %. The manganese helps
to substitute for nickel up to about 2 % and acts as an austenite stabilizing
addition above about 2 %. Manganese acts as a deoxidizer during refining and
2 0 tends to combine with any sulfur present to form chromium rich manganese
sulfides. This form of sulfides is favorable over other sulfide forms for good
corrosion resistance and machinability.
The chromium content of the steels of the invention is in the range of
about 13 to about 17 % and preferably about 14 to about 16 %. The chromium
2 5 content is balanced with austenite forming elements to provide the desired
martensitic structure. This balance provides the desired corrosion resistance
and
hardness as well. Chromium is prefErrably maintained at as low a level as
possible to meet the desired properties and keep the alloy economical. The
optimum chromium is about 14.5 to about 15.5 %.
3 0 Copper is an essential addition to~ the steels of the invention to permit
the
reduction in nickel content and stabilize a portion of the austenite. The
present
copper level does not require the nickell relationship of U.S. 4,314,863
wherein
the sum of the nickel and copper must b~e at least about 5 % and a copper
range
of about 2.0 to 3.5 % is present to provide the desired as-cast hardness. The
3 5 copper content of the present inventions is from about 1.5 to about 4.0 %
and
preferably about 2.0 to about 3.5 % but does not have the same relationship
with
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2055154
nickel. The optimum combination of properties is provided when the copper
ranges from about 2.5 to about 3.25 %. Copper additions in the upper part of
the
range, such as about 3.0 to about 4.~0 % may be used to provide the softest
material within the ranges of the invention. With proper heat treatment, the
well
known age hardening effects of copper may be utilized.
Nickel is restricted to levels below 1.0 % to reduce the alloy cost of the
material. Preferably, the nickel is below about 0.9 % and more preferably
below
about 0.75 % and still more preferably below 0.5 %. Nickel is replaced by
additions of carbon, nitrogen, copper and manganese in the present
1 0 composition. The nickel present does contribute to the hardness,
austenite, and
notch toughness of the alloy.
Silicon is present in the steel in an amount ranging up to about 1.0 %.
Preferably silicon is present at a level below about 0.75 %. Silicon acts as a
deoxidizer during refining and tends to improve the fluidity and castability
of the
1 5 molten metal. Higher levels of silicon would require additions of
austenite
forming elements to balance the structure which tends to increase the cost of
the
alloy and does not appear to provide any substantial benefits. Silicon
contents
above about 1.0 % may tend to cause low ductility in any ferrite present which
contributes to fracture.
2 0 Molybdenum is present in an amount up to about 1.0 % and preferably is
maintained at residual levels up to about 0.75 %. A more preferable range is
to
maintain the molybdeum below about 0.5 %. When the alloy is used for marine
applications, it may be preferable to maintain the molybdenum nearer the upper
limits of the ranges for improved corrosion resistance.
2 5 Boron is optional in the present alloy system but does seem to provide
some benefits for improved hot working. When present, boron should be in the
range of about 0.001 to about 0.003 %.
Sulfur is maintained at levels below about 0.03 % and typically at levels
below about 0.02 % for improved corrosiion resistance. In some situations,
sulfur
3 0 could range as high as about 0.5 % if better machinability were needed. A
preferred range for sulfur in free - machining applications is about 0.1 to
about
0.5 %.
Phosphorus is maintained at levels below about 0.03 % and preferably
below about 0.025 %.
3 5 An optional addition is the use of niobium, titanium, vanadium and / or
zirconium for improved ductility in amounts up to about 0.5 % to provide
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improved grain refinement in wrought products. It has been determined to have
very little value in castings and tends to increase the cost of the alloy.
Boat propellers are typically cast from stainless steels such as 15-5PH,
17-PH and T 431 and require good corrosion resistance including corrosion
fatigue resistance, a hardness of about Rockwell C 25 to about C 35 and good
machinability. The present alloy is particularly well suited for marine
articles
such as boat propellers.
Various wrought products such as sheet, strip, bar, rod, wire, billets,
blooms and slabs may be produced 'from the steels of the present invention.
1 0 These martensitic steel articles possess the excellent combination of
properties
of the invention also. Forgings, including forged golf club heads and cutlery
applications, may also be manufactured from the steels of the invention.
The data in Table 1 below reports the various compositions studied
during the investigations of the present invention. The materials were air
1 5 induction melted and represent typical remelt stock used for investment
casting.
25
35

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TABLE 11
Chemical Analysis of Materials (Weight %)
Steel ~ ~ ~ s~ ~i SC Ly.i,~1 rl ~
A1 * .041 2.16 .018 .007 .76 14.77<.1 2.83 .074
A2* .042 2.13 .018 .007 .76 15.09<.1 2.82 .087
A3* .042 2.15 .017 .008 .79 15.31<.1 2.82 .090
B 1 * .040 4.14 .018 .007 .89 14.98<.1 2.80 .072
B2* .041 4.12 .017 .006 .91 15.22<.1 2.79 .086
B3* .040 4.12 .018 .006 .94 15.39<.1 2.80 .100
C1 * .040 1.99 .022 .013 .64 15.11 <.1 3.10 .085 .15 .001
C2* .0361.94 .022 .008 .65 15.08 <.1 3.11 .084 .21 .002
C3* .0351.92 .022 .006 .67 15.12 <.1 3.11 .084 .30 .002
D 1 * .0362.12 .022 .008 .66 15.07 1.003.13 .089 .15 .002
D2* .0362.08 .022 .008 .66 15.10 1.013.13 .089 .22 .002
D3* .0362.02 .021 .008 .64 15.10 1.003.12 .090 .30 .001
E* .0612.04 .020 .008 .78 15.24 0.523.19 0.092
2 0 F1 * .0392.21 .024 .003 .68 15.26 1.013.11 .056
F2* .0383.11 .025 .003 .64 15.25 1.003.07 .057
F3* .0393.68 .024 .003 .63 15.16 1.003.06 .056
T431 .13 0.64 .017 .008 .52 16.15 2.040.14 .049
17-4PH .0380.54 .017 .008 .55 16.21 4.133.11 .045
2 5 *Steels on
of the
Inventi
TABILE 1 A
Chemical Analyses of Golf Irons (Weight %)
Alloy
3 0 st IXRS SS ML P ~ ~i ~ C .di Sue.
ee I
G 431 .096 0.92 .028 .00910.9815.16 1.54 .14 .23
H 431 .126 0.67 .023 .008 1.1616.12 1.56 .20 .065
I .121 1.11 .030 .006 1.4116.33 4.26 .22 .23
J 304 .082 1.30 .040 .006 0.7617.85 8.66 .99 ----
3 5 K 431 .090 0.50 .019 .079 0.6814.81 1.51 .18 .015
All stee ls
had
residual
nitrogens
11

2055154
Steel E of the invention from Table 1 was evaluated for mechanical
properties and the results are shown in Table 2. The cast tensile specimens
were tested in the as-cast condition and after softening at 1300°F (
705°C ) for 1
hour with air cooling. Data on 17-4P'H was included for comparison purposes.
Both alloys exhibited limited ductility in the as-cast condition. The
1300°F
( 705°C ) treatment provided a good combination of strength and
ductility.
Modified heat treatments were conducted for hardness testing and the results
are shown in Table 3. All the heat treatments for Table 2 and Table 3 were for
1
hour and air cooled except where noted. Duplicate samples of Steel E were
tested.
IABLE 2
Mechanical Properties
1 5 UTS .2% YS % EI.
Rockwell
Steel ~ ~ tg r n ~
E - As-Cast 165.5 115.7 O.G. 2.5 C39.5
2 0 E - As-Cast 150.0 109.9 2.2 2.4 C40.3
1300F-1 Hr. 119.9 96.4 12.1 38.7 C25.5
1300F-1 Hr. 122.1 96.8 15.8 45.8 C24.5
2 5 17-4 PH 135 128 1 6 C32
As-Cast
O.G. - Broke out of gage length
12

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I~BLE 3
Effect of Heat TrE3atment on Hardness
Condition A1 A2 .A~ ~1 ~2 ~ Tvr'" a 431 17-4 PH
Cast STEEL E 35 36 38 37 36 36 44 36
Cast + 1150°F (620°C) ___ -__ ___ ___ ___ ___ ___ 30
Cast + 1200°F (650°C) 25 26 26 28 27 29 --- 29
Cast + 1250°F (675°C) 24 23 25 26 27 28 --- 31
Cast + 1300°F (705°C) 22 22 23 26 26 28 --- 32
1 0 Cast + 1900°F (1040°C) 38 40 40 38 39 39 --- 36
Cast + 1900°F (1040°C)
+ 1350°F (730°C) 21 22 22 26 26 28 --- 31
.Cast + 1800°F - .5 Hr --- --- --- --- --- --- 25 ---
Cast + 1350°F (730°C) --- B98 --- --- --- --- --- -__
1 5 Cast + 1400°F (760°C) --- B97 ~--- --- --- --- --- ___
Cast + 1450°F (785°C) ___ B98 .-__ ___ ___ ___ ___ ___
Cast + 1500°F (815°C) --- 25 ~--- --- --- --- --- ___
All values were Rockwell C except whE3re noted.
The results of the hardness teats shown in Table 3 clearly indicate the
2 0 present steels of the invention may hardened to a wide range of values
from B
97 to C 40 as desired. To soften the alloy by increasing the level of ferrite
is
easily obtained with the martensitic steels of the invention.
One of the properties of interesll for the steels of the invention is
ductility.
To evaluate this property with steels treated at different temperatures, a
series of
2 S investigations was conducted and reported in Table 4. Various steels were
heat
treated at temperatures from 1050°F to 1500°F ( 565°C to
815°C ) to determine
the ductility as measured by bend test:>. The thickness of the materials were
0.1
inches ( 0.25 cm ) and the ratios were determined by dividing the bend
diameter
by the specimen thickness. Material having no cracks was identified with a P
for
3 0 passing and when cracks were observed, with an F for failing. The results
indicate that the steels of the invention possess good ductility when the
appropriate heat treatment for the desired properties is selected.
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TABLE 4
Bend T~sst Results
Steel 1850F11~gF 1150F1200F I~.~E 1~E 14~E 14~E 1508F
12~5~
A1 RC 31 RC 28 RC RC RC 22
26 23
F-4T F-4T P-4T P-4T P/F-3T
P-5T
A2 RC 22 Rg 98 Rg 97 Rg 98 R~25
F-3T P-4T P-4T P-4T F-5T
P-4T P-5T P-5T P-5T F-6T
P-5T
A3 RC 23
F-3T
P-4T
1 P-5T
5
B 1 R~ 26
F-3T
P-4T
P-5T
2 B2 R~ 2s
0
F-3T
F-4T
P-5T
B3 RC 28
2 F-3T
5
F-4T
P-5T
C1 RC 29 RC R~ RC 23
27 25
F-4T F-4T F-4.T F-4T
3 F-5T F-5T F-5T P-5T
0
C2 RC 28 RC RC RC 21
26 24
F-4T F-4T F-4.T F-4T
F-5T F-5T F-5T P-5T
14

20 5 515 4
TABLES 4 '(Con
Bend Test Results
Steel 50F 110F 1150F12~~F l2ySLE 1~9E 1350F 1400F 1450F
150F
5 C3 RC 27 R~ 25 R~ 23 Rg 97
F-4T F-4T F-4T F-4T
F-5T F-5T F-5'T P-5T
D1 R~ 34 R~ 32 R~ 30 RC 27
F-4T F-4T F-4'T F-4T
10 F-5T F-5T F-5'f F-5T
D2 RC 34 R~ 32 R~ .30 RC 27
F-4T F-4T F-4'f F-4T
F-5T F-5T F-5'f F-5T
D3 RC 34 RC 32 RC 29 RC 27
1 F-4T F-4T F-4-f F-4T
S
F-5T F-5T F-5-f F-5T
T431 - 1800F - 1/2 RC 25 F-3T; P-4T; P5T
hour
17-4 - 1300F - 1 RC32 F-3T; F-4T; P/F-5T
PH hour
2 17-4 - 1150F - 4 RC30 F-3T; P-4T; P-5T
0 PH hours
The stainless steel composition and articles made from the composition of
the present invention have produced a combination of properties not previously
available with an economical balance of elements. The alloy balance is easily
2 5 heat treated to provide a broad range of properties to suit many
applications.
Additions to the basic alloy composition which do not significantly influence
the
basic properties of the steel are considered to be within the broader aspects
of
the invention. A broad range of heat treatments are also considered within the
teachings of the present disclosure wlhich may be selected depending on the
3 0 desired properties.
While the present invention has been described in terms of the stainless
steel composition and the production of various cast, forged or wrought
articles,
the steels and articles have a good combination of properties suited for many
other applications. It will be understood that various modifications can be
made
3 5 to the invention without departing from the spirit and scope of it.